prevert ast errors from being normalized before ast_error_finish is called (closes #15846)

1 files changed, 8 insertions, 0 deletions

diff --git a/Python/ast.c b/Python/ast.c
index 6faf5b21a6..3d0e3844b7 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -92,7 +92,15 @@ ast_error(const node *n, const char *errstr)
     PyObject *u = Py_BuildValue("zii", errstr, LINENO(n), n->n_col_offset);
     if (!u)
         return 0;
+    /*
+     * Prevent the error from being chained. PyErr_SetObject will normalize the
+     * exception in order to chain it. ast_error_finish, however, requires the
+     * error not to be normalized.
+     */
+    PyObject *save = PyThreadState_GET()->exc_value;
+    PyThreadState_GET()->exc_value = NULL;
     PyErr_SetObject(PyExc_SyntaxError, u);
+    PyThreadState_GET()->exc_value = save;
     Py_DECREF(u);
     return 0;
 }